Non-aqueous electrolyte secondary batteries such as a lithium ion secondary battery are widely used as batteries for use in personal computers, cellular phones, portable information terminals and so on.
In a non-aqueous electrolyte secondary battery, a separator is generally used as a member for separating a positive electrode and a negative electrode. Conventionally, a porous membrane formed of polyolefin have been used as a separator, there is a problem that heat resistance is not satisfactory.
As a separator having excellent heat resistance, for example, Patent Document 1 proposes a separator having a porous membrane formed of a metal oxide and polyvinyl alcohol.